package com._23DesignPattern._algorithm._sort;

import org.apache.commons.lang3.ArrayUtils;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

/**
 * @Author: huangya
 * @Date: 2019/5/7
 * @Description:
 */
public class MergeSort {

    static int SIZE = 20000;

    private static List<Integer> list = new ArrayList<>(SIZE);
    private static Integer[] integers = new Integer[SIZE];
    private static int[] ints = new int[SIZE];

    static {
        for(int i=0;i<SIZE;i++){
            list.add(i);
        }
        Collections.shuffle(list);
        integers = list.toArray(integers);

        ints = ArrayUtils.toPrimitive(integers);

    }

    public static void main(String []args){
        long start = System.currentTimeMillis();
        sort(ints);
        System.out.println(Arrays.toString(ints));
        System.out.println();
        BinaryTree binaryTree = new BinaryTree();
        System.out.println();
        long end = System.currentTimeMillis();
        System.out.println(end-start);
    }
    public static void sort(int []arr){
        int []temp = new int[arr.length];//在排序前，先建好一个长度等于原数组长度的临时数组，避免递归中频繁开辟空间
        sort(arr,0,arr.length-1,temp);
    }
    private static void sort(int[] arr,int left,int right,int []temp){
        if(left<right){
            int mid = (left+right)/2;
            sort(arr,left,mid,temp);//左边归并排序，使得左子序列有序
            sort(arr,mid+1,right,temp);//右边归并排序，使得右子序列有序
            merge(arr,left,mid,right,temp);//将两个有序子数组合并操作
        }
    }
    private static void merge(int[] arr,int left,int mid,int right,int[] temp){
        int i = left;//左序列指针
        int j = mid+1;//右序列指针
        int t = 0;//临时数组指针
        while (i<=mid && j<=right){
            if(arr[i]<=arr[j]){
                temp[t++] = arr[i++];
            }else {
                temp[t++] = arr[j++];
            }
        }
        while(i<=mid){//将左边剩余元素填充进temp中
            temp[t++] = arr[i++];
        }
        while(j<=right){//将右序列剩余元素填充进temp中
            temp[t++] = arr[j++];
        }
        t = 0;
        //将temp中的元素全部拷贝到原数组中
        while(left <= right){
            arr[left++] = temp[t++];
        }
    }
}
